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MCQ practice · SSC Higher Mathematics Board questions · Chapter 1: Set and Function

Cumilla Board 2024

If A and B are sets, which expresses A \ B in set builder form?

Think it through first, then pick an option.

  1. a {x : x ∈ A and x ∈ B}
  2. b {x : x ∈ A or x ∈ B}
  3. c {x : x ∈ A and x ∉ B}
  4. d {x : x ∈ A or x ∉ B}
Answer and explanation

Correct answer: c {x : x ∈ A and x ∉ B}

Definition: A \ B = {x : x ∈ A and x ∉ B}.

Why the other options are wrong

  • a {x : x ∈ A and x ∈ B}: That is A ∩ B; a difference removes the elements of B, so it needs x ∉ B.
  • b {x : x ∈ A or x ∈ B}: That is A ∪ B; A \ B needs x ∈ A and x ∉ B.
  • d {x : x ∈ A or x ∉ B}: With 'or', elements outside A would get in; a difference needs 'and'.